Hi Peter DB2OS,
Thank you very much for your precise step by step satellites history explanation.....hoping that the human community can learn from these mistakes and never repeat these more.... ..waiting for P3-E and P5-A and ...."fingers crossed"...
73' Frank IW4DVZ
-----Messaggio originale----- Da: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] Per conto di Peter Guelzow Inviato: lunedì 9 febbraio 2009 23.49 A: amsat-bb@amsat.org Oggetto: [amsat-bb] Re: Was HEO naivete; now GEO rideshare frequency choice, etc.
P3-B Someone forgot that P3-B (OSCAR-10) was hit by the last rocket stage of the launcher, when they neutralized that stage by venting the remaining fuel. Unfortunatly in the wrong direction... OSCAR-10 was hit, Antennas were damaged, the S/C spin was reverse (!) and the sun was shining on top of the spacecraft instead of illuminating the solar panels !!! The S/C was completely out of control, loosing rapidly it's battery capacity, getting into harsh temperatures due to totally wrong sun angles and thermal control... The S/C would have been dead and lost, if Karl Meinzer DJ4ZC would have not started his amazing rescue operation by completely re-programming the IHU on-the-fly. First he switched Off all modules and systems which were not urgently needed... he also programmed the beacon off and only sends some telemetry after a few hours... this way he was able to slowly re-charge the battery. Finally there was enough electrical energy to start magnetorqueing and bringing the S/C into the right attitude. But due to the fact that the S/C was spinning "backwards", he had to write and upload new navigation code into the IHU.... After several weeks of emergency, finally AO-10 was in a favorable orbit to continue commissioning and bringing the S/C into the right attitude for raising the perigee.. if we would have waited too long, perigee would get too close and the bird would have had other problems..
During the above emergency, the fuel tanks and helium bottle had some thermal cycles which were out of the designed specification limits....
Everyone will agree, that this was not the fault of the designer of P3-A.... any other spacecraft would have been lost...
The "small deviation" mentioned below was not a design error... to my knowledge two bit's in the SEU's programmable register to set the burn-time counter were exchanged (wrongly wired in the module to the connector to the IHU) and the test pattern which was used for testing did not showed this... Due to the longer than planned burn-time, the Helium bottle temperature went shortly below the lower specified limit. Again, this was not a design flaw or any other mistake... One can argue if the burn-counter-problem or the emergency caused by the collision with the last rocket stage after seperation caused the leakage in the high pressure helium system... but that's history anway..
P3-C (OSCAR-13) The propulsion system worked perfectly and the planned orbit was reached exactly. Several experts (including from NASA) were involved in the planning of OSCAR-10's orbit, which was supposed to be safe / stable for a long long time...... Only several years later, OE1VKW Viktor Kudielka was so first one who predicted a premature re-entry of OSCAR-13... Kudielka V., /Long term Predictions for Highly Elliptic Satellite Orbits/, Amsat-DL Journal, Jun 1990. pps 5-7. (In German). Nobody can be blamed... but a lot was learned after this discovery, even in the professionally world..
P3-D (OSCAR-40) The catastrophic failure of the propuslion system was not a design error, it was 100% human failure... The 400N engine was the same which was used before on AO-10 and AO-13. Unfortunately "almost".. the engine which was donated to us, was used for some qualification tests, but 100% functional and 100% OK.. But it had a small modification used for the qualification.. a venting hole, which was secured with an additional screw or cap.. normally it's just a hole.. only very few people knew about it and unfortunately nobody asked what it was, although it was "red".... during the final and launch integration this was hidden and nobody noticed it. During some early testing in the integration lab in Florida, this valve was never used at it was recommended to not use it too often during "dry test" for reliability issues.. Later during our intense failure analysis we found a picture from the earlier integration phase, which showed the engine valve with this red cap in place.... arghhh... After the first sign of a malfunction of the engine, it would have been better to take more time to analyze the behavior... but there was some kind off pressure and afterwards everybody knows it better anyway.. I can only tell, that the the process which resulted in the catastrophic engine failure was completely understood in the aftermath... And still... we had almost 4 years to work with this wonderful spacecraft on S-band... even with very small antennas... most of the technology we wanted to test were successfully tested and proofed, including the Arcjet which was used to raise the perigee, the momentum wheels, etc... the discovery of an additional (temorary?) radiation belt was also due to AO-40's CEDEX... and so on...
However, if you ever want another HEO, than there is no way around a propulsion.... As with P3-D some well known companies which design propulsion systems will be involved in the design and qualification of P3-E and P5-A's propulsion system....
73s Peter DB2OS
Nigel Gunn G8IFF/W8IFF wrote:
Paul Williamson wrote:
"The first burn went relatively well -- there was a small deviation from the
expected burn duration, which placed the spacecraft perigee somewhat higher
than planned. The second burn could not be accomplished because a slow leak in
the high-pressure helium system during
the week the spacecraft was being reoriented prevented the opening of valves feeding fuel to the thrust
assembly."
The "small deviation" is known to be due to a design error in the simple
digital logic circuit that controlled the burn duration.
OK. The helium leak was a propulsion system fault. The design error in the
logic was human error and is known so can be
designed out.
On AO-13, the kick motor worked exactly as planned, and the spacecraft
achieved the intended orbit. But that orbit could have been chosen better,
as it turned out. The early re-entry after only 8.5 years was not anticipated,
and probably could have been avoided if
we had been smart enough, soon enough.
Another "human error" Hindsight is wonderful. I don't think we should reject an option that requires propulsion because of
past errors that are now well understood.
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